Prius Generator Conversion Process

Prius Household Back-up Generator Development Process


After extensive research and reading postings on this and other forums I have arrived at the following plan to use my 2011 Prius Two, not II, as a back-up generator for my house.


This is still in the R&D stage and I appreciate any comments, suggestions etc. in order to make it more useful. Feel free to use it in your endeavors.


Tools


6, 10 and 12mm sockets, Phillips screw driver and a 10mm wrench, electrical tape, drill, soldering iron, hacksaw, heavy rubber insulated gloves .


Pre Installation Procedure

1. Confirm that the amperage of needed power does not exceed the generator's capacity.
   
   
2. The combined amperage may exceed the generator's capacity as long as the instruments aren't running simultaneously.
   
   
3. Assign each appliance a number which coincides with its circuit and label this in the circuit breaker of the switch.
   
   
4. The sizes of the assigned breakers must be equal in both the transfer switch and the home's load center.
   
   
5. Cut the main power supply.
   
   
6. Wear the rubber gloves.

Steps: Installation of the inverter, inlet box and Transfer Switch

1. Open the Prius hatch. Remove the floor mats and storage shelf
   
   
2. Locate the cover and batteries near the rear seat. wear thick rubber gloves throughout the rest of the process to avoid electrocution. (This is a 220v battery pack.)
   
   
3. Remove the battery cover.
   
   
4. Use a soldering iron and a hacksaw to cut the plastic leg off the bottom of the battery cover.
   
   
5. DISCONNECT THE NEGATIVE BATTERY CABLE from the traction/HV battery first AND TUCK IT OUT OF THE WAY.
   
   
6. Crimp and solder 5/16 heavy gauge eye terminals to 2 awg foot-long wires (red to positive black to negative)and install on the posts of the HV battery.
   
   
7. Affix a to the other ends of these wires.
   
   
8. Crimp and solder the prongs of a 75 amp plug connector the other half of these wires,
   
   
9. Crimp and solder the prongs of the other half of the connector to the ends of foot long red and black 2 awg wires, and eye terminals to the other ends.
   
   
10. Bolt the eye terminals to a 5,000 watt, LF, Pure Sine Wave, DC 12V to AC 220V & 110V, 60HZ inverter.
    
    
11. Install a 100 Amp breaker in the positive wire between the inverter and the battery.
    
    
12. Or another way to setup a Prius generator is to use industrial UPS that matches the Prius's HV battery voltage. This will bypass the step down converter. It's taking power directly from the HV battery. If it goes low, the engine kicks in to charge the HV battery.
    
    
13. Use the battery hold down bolt as the earth ground, and connect it now.
    
    
14. Cover any exposed terminal material, with electrical tape or liquid electrical tape.
    
    
15. Reconnect the positive battery cable.
    
    
16. Leave the negative battery cable disconnected until the entire generator installation process is complete.
    
    
17. Make sure that the wires clear everything they can rub against so they won’t loosen or the insulation won’t wear through. Cover exposed terminals.
    
    
18. Mount a inlet box on the garage wall so it sticks through the basement wall at an appropriate location.
    
    
19. Mount a 6-10 circuit, manual, 30 amp safety transfer switch with circuit breakers that match the circuits of the house that you want to augment on the basement wall within 5 feet of the main circuit breaker box.
    
    
20. Install the ends of a 10-2 awg cable on the terminals of the inlet box.
    
    
21. Run the wire through PVC conduit to the transfer switch and install a 50-80 amp relay and breaker in the red and black wires of this cable.
    
    
22. Attach the ends of this cable to the lugs of a 60 amp main breaker in the switch.
    
    
23. Take the cover off the main circuit panel.
    
    
24. Run the wires from the breakers in the transfer switch to the lugs of the appropriate breakers in the Main circuit breaker panel. Scrim ⅝” off the end of each wire. Loosen the screw of each of the lugs in turn and Slide the bare end of the wire into the hole. Tighten the screw.
    
    
25. Mount the inverter to the floor of the Prius’s hatch so it will not move around as I drive. Mark and drill holes in the plastic for the mounting screws and nuts. Make sure to leave enough room to get to the screws. Cover the wires with plastic protectors.
    
    
26. Plug the cable from the inlet box into the inverter.
    
    
27. Once everything is installed reattach the negative battery cable
    
    
28. While the main power is still off trip the breakers to all circuits attached to the transfer switch except one with the least wattage. Test the system by starting the car while it runs, check the temperatures of every connector and breaker. Do that for each circuit. As you approach the load limit, the breaker and the connectors should get warm but not to hot to touch. If they get hot recrimp them.
    
    
29. Install the battery cover, storage shelf, and floor mats.

Supplementary Comments/Suggestions Regarding the Prius Generator Project


This is a fairly difficult project that takes up to 8 hours once you have all the plans, tools and equipment ready for installation.


Most of it entails installation that should be relatively easy for an average handyman. Connecting wiring to the transfer switch and main circuit panel can be quite dicey if you don’t know exactly what you’re doing. So for these elements al least consult with a professional electrician or have them do it. If a professional electrician installs the entire thing it will cost between $500 to $800.00.


Connecting the 2 awg wires to the HV battery if not done with the utmost caution can get you fried, remember the output is 220v DC. Wear rubber gloves for this operation.

The equipment including wiring, the inverter, transfer switch, connectors and PVC conduit will cost between $700 and $1,000.00 depending upon wattage and where you purchase it. I am purchasing most everything through Ebay.Purchase the transfer switch as a kit including the pre wired switch, inlet box, 10 foot power cord and 6 breakers for about $300.00. Inverters run about $300 for a 3000w, LF, pure sine wave, 110/220v 60hrz to $450.00 for a 5000w inverter. I don’t know which company produces the best of each but almost all are made in China.


The combination of a inverter and transfer switch will cost the same as for a gas powered generator and transfer switch (transfer switch is a must either way). Of course if you don’t already have a Prius or other hybrid the cost will be considerably more for the Prius generator. The prius sits in the garage while the generator must sit outside and the generator is extremely noisy while the Prius is quiet.


The Prius exhaust must be vented via a hose through the garage wall.


Toyota offers a factory-installed option available for between $800 and $1,200 on top of the vehicle price. Rated at 1.5kW, the Toyota system offers, either in-car 120V outlets, or an adapter that plugs into the charge port.

ConVerdant Vehicles offers 2kW-5kW Plug-Out Kits. ConVerdant has kits for the Prius c and Prius Plug-In, which use different batteries. These kits cost over $1000 for the 3kW and $2000 for the 5kW kit. On eBay inverters cost about $300 for a new 3kW inverter and $350 for a 5kW inverter.


These systems still need the transfer switch kit and related wiring. The Toyota system provides only 1500 watts of power. One reviewer paned the ConVerdant system as being an inverter in a big plastic box. I really don’t know what is inside but I don’t think it’s a UPS, uninterruptible power supply, including batteries that may justify the price.

 

Prius Household Back-up Generator Development Process


After extensive research and reading postings on this and other forums I have arrived at the following preliminary plan to use my 2011 Prius II as a back-up generator for certain circuits in my house.


I am getting old so I need to make my directions as detailed as possible so I don’t forgot anything. This is still in the R&D stage and I appreciate any comments, suggestions, etc. in order to make it more useful. Feel free to use it in your endeavors.


Tools


6, 10 and 12mm sockets, Phillips screw driver and a 10mm wrench, electrical tape, drill, soldering iron, hacksaw, heavy rubber insulated gloves .


Pre Installation Procedure

1. Confirm that the amperage of needed power does not exceed the generator's capacity.
   
   
2. The combined amperage may exceed the generator's capacity as long as the instruments aren't running simultaneously.
   
   
3. Assign each appliance a number which coincides with its circuit and label this in the circuit breaker of the switch.
   
   
4. The sizes of the assigned breakers must be equal in both the transfer switch and the home's load center.
   
   
5. Cut the main power supply.
   
   
6. Wear the rubber gloves.
   
   
7. Consult with an electrician about the process and have him take on the appropriate steps.
   

Steps: Installation of the inverter, inlet box and Transfer Switch

1. Open the Prius hatch. Remove the floor mats and storage shelf
   
   
2. Locate the cover and batteries near the rear seat. Wear thick rubber gloves throughout the rest of the process to avoid electrocution. (This is a 220v battery pack.)
   
   
3. Remove the battery cover. Pull out the orange disconnect on the HV battery. UTube has a great video on how to remove the cover and install the necessary cables for the inverter on a generation III Prius.
   
   
4. Use a soldering iron and a hacksaw to cut the plastic leg off the bottom of the battery cover.
   
   
5. DISCONNECT THE NEGATIVE BATTERY CABLE from the 12V battery first AND TUCK IT OUT OF THE WAY.
   
   
6. Crimp and solder 5/16 heavy gauge eye terminals to 2 awg foot-long wires (red to positive black to negative)and install on the posts of the HV battery.
   
   
7. Affix a to the other ends of these wires.
   
   
8. Crimp and solder the prongs of a 75 amp plug connector the other half of these wires,
   
   
9. Crimp and solder the prongs of the other half of the connector to the ends of foot long red and black 2 awg wires, and eye terminals to the other ends.
   
   
10. Bolt the eye terminals to a 3kW or 5kW, LF, Pure Sine Wave, DC 12V to AC 220V & 110V, 60HZ inverter.
    
    
11. Install a 50 Amp self reset breaker in the positive wire between the inverter and the battery.
    
    
12. Or another way to setup a Prius generator is to use industrial UPS, uninterruptible power supply, that matches the Prius's HV battery voltage. This will bypass the step down converter. It's taking power directly from the HV battery. If it goes low, the engine kicks in to charge the HV battery.
    
    
13. Use the battery hold down bolt as the earth ground, and connect it now.
    
    
14. Cover any exposed terminal material, with electrical tape or liquid electrical tape.
    
    
15. Reconnect the positive and negative battery cable.
    
    
16. Leave the negative battery cable disconnected until the entire generator installation process is complete.
    
    
17. Make sure that the wires clear everything they can rub against so they won’t loosen or the insulation won’t wear through. Cover exposed terminals.
    
    
18. I’m using a manual transfer switch with an inlet box and L14-30, 10-4 awg, 250v power cable to connect the inverter to my main breaker panel vs using extension cords. However the inverter has a 3 wire AC output receptacles and the power cord has a L14-30 4 wire male plug and screw terminals. So I will take about a foot long piece of 10-4 awg 4 wire 250V cable, attache a L14-30 female plug to one end and hardwire the othe end to the inverter.
    
    
19. Mount a inlet box on the garage wall so it sticks through the basement wall at an appropriate location.
    
    
20. Mount a 6-10 circuit, manual, 30 amp safety transfer switch with circuit breakers that match the circuits of the house that you want to augment on the basement wall within 5 feet of the main circuit breaker box.
    
    
21. Install the ends of a 10-2 awg cable on the terminals of the inlet box.
    
    
22. Run the wire through PVC conduit to the transfer switch and install a 50-80 amp relay and breaker in the red and black wires of this cable.
    
    
23. Attach the ends of this cable to the lugs of a 60 amp main breaker in the switch.
    
    
24. Take the cover off the main circuit panel.
    
    
25. Run the wires from the breakers in the transfer switch to the lugs of the appropriate breakers in the Main circuit breaker panel. Scrim ⅝” off the end of each wire. Loosen the screw of each of the lugs in turn and Slide the bare end of the wire into the hole. Tighten the screw. (I will have a professional electrician do this.)
    
    
26. Mount the inverter to the floor of the Prius’s hatch so it will not move around as I drive. Mark and drill holes in the plastic for the mounting screws and nuts. Make sure to leave enough room to get to the screws. Cover the wires with plastic protectors.
    
    
27. Plug the cable from the inlet box into the inverter cable.
    
    
28. Once everything is installed reattach the negative battery cable.
    
    
29. While the main power is still off trip the breakers to all circuits attached to the transfer switch except one with the least wattage. Test the system by starting the car while it runs, check the temperatures of every connector and breaker. Do that for each circuit. As you approach the load limit, the breaker and the connectors should get warm but not to hot to touch. If they get hot recrimp them.
    
    
30. Install the battery cover, storage shelf, and floor mats.
    

Supplementary Comments/Suggestions Regarding the Prius Generator Project


This is a fairly difficult project that takes up to 8 hours once you have all the plans, tools and equipment ready for installation.


Most of it entails installation that should be relatively easy for an average handyman. Connecting wiring to the transfer switch and main circuit panel can be quite dicey if you don’t know exactly what you’re doing. So for these elements al least consult with a professional electrician or have them do it. If a professional electrician installs the entire thing it will cost between $500 to $800.00.


Connecting the 2 awg wires to the HV battery if not done with the utmost caution can get you fried, remember the output is 220v DC. Wear rubber gloves for this operation.


The equipment including wiring, the inverter, transfer switch, connectors and PVC conduit will cost between $700 and $1,000.00 depending upon wattage and where you purchase it. I am purchasing most everything through Ebay.Purchase the transfer switch as a kit including the pre wired switch, inlet box, 10 foot power cord and 6 breakers for about $300.00. Inverters run about $300 for a 3000w, LF, pure sine wave, 110/220v 60hrz to $450.00 for a 5000w inverter. I don’t know which company produces the best of each but almost all are made in China.


The combination of a inverter and transfer switch will cost the same as for a gas powered generator and transfer switch (transfer switch is a must either way). Of course if you don’t already have a Prius or other hybrid the cost will be considerably more for the Prius generator. The prius sits in the garage while the generator must sit outside and the generator is extremely noisy while the Prius is quiet.


The Prius exhaust must be vented via a hose through the garage wall.


Toyota offers a factory-installed option available for between $800 and $1,200 on top of the vehicle price. Rated at 1.5kW, the Toyota system offers, either in-car 120V outlets, or an adapter that plugs into the charge port.

ConVerdant Vehicles offers 2kW-5kW Plug-Out Kits. ConVerdant has kits for the Prius c and Prius Plug-In, which use different batteries. These kits cost over $1000 for the 3kW and $2000 for the 5kW kit. On eBay inverters cost about $300 for a new 3kW inverter and $350 for a 5kW inverter.


These systems still need the transfer switch kit and related wiring. The Toyota system provides only 1500 watts of power. One reviewer paned the ConVerdant system as being an inverter in a big plastic box. I really don’t know what is inside but I don’t think it’s a UPS, uninterruptible power supply, including batteries that may justify the price.

 

Does your system use a 12v, 24v or 48v inverter? A 3000w or 5000w, SP, LF, 220v/110v. In other what are your inverter and Transfer switch specifications.

Thanks for the comments/suggestions. I thought I would go with either a 3000w or 5000w pure sine wave, LF, 220v/110v (240/120) inverter. I have read that the Prius HV battery and system outputs a max of 3000w so I am leaning toward 3000w with a max of 9000-12000w. 5000w seems excessive. I am undecided on 3000 vs, 5000, and 12v Vs 24 or 48. So your 48v comment is appreciated. I know the HV battery output 210-235vdc but thought that since it is connected to a 12v battery 12v would be appropriate.

The transfer switch I am considering is a Generac Power Systems Portable Generator # 6294 Transfer Switch Kit Includes : 30A Prewired Transfer Switch, 30A Non-Metallic Power Inlet Box, a 4 wire, 10' Power Cord With L14, 30 Ends and Accommodates 6 To 10 Circuit breakers. See my original thread for installation. I am planning on consulting with an electrician before I finalize my system and having them do the critical wiring.

 

I have read almost every thread on the use of a Prius as a generator and have published a initial procedure for review. I have received great feedback from rjparker. I have seen a procedure for using the HV battery, an inverter, a transfer switch/inlet box, L14-30 power cord and main breaker panel. What I derive from all threads is this can only be done using the Converdant Vehicles system. That is because the HV Prius battery is 220v so you need a 220vdc or larger (PSW, LF, SP 220vac/110vac) inverter. I am inquiring if Converdant even uses a Transfer switch and what vdc their inverter is. I have checked their site and list of specifications but found no reference to these elements. I also can’t find much on how to wire an inverter to a transfer switch or inlet box.


Using the 12v battery won’t work for me. We live in an all electric condo. I have decided to isolate most of our baseboard heating elements. from the backup system because they use from 500 to 2000 watts.


Does anyone have any details regarding how to wire an inverter to a transfer switch- plugs, vs. hard wiring, three vs four wires and what VDC inverter to use.

 

What I derive from all threads on this topic is this can only be done using the ConVerdant Vehicles system kit. That is because the HV Prius battery is 220v so you need a 220vdc or larger (PSW, LF, SP 220vac/110vac) inverter. I am inquiring through email about the vdc of ConVerdant’s inverter. I have checked their site and list of specifications but found no reference to these elements. I haven’t received a response from them yet.

ConVerdant, seems to have a monopoly on the inverters that can be used for this purpose and they're charging $2,000 for a 5 kW inverter. Once you add the cost of the transfer switch and installation you're up around $3,000 to maybe $4,000 for the system. Given the fact that our area hasn’t experienced any long power outages yet I am in a quandary as to whether not to spend that much money on basically an insurance program.

Since I will have an electrician wire the transfer switch to the main panel that is not issue.

Does anyone have any details regarding how to wire an inverter to a transfer switch/inlet box- plugs, vs. hard wiring, three vs. four wires and what VDC inverter to use. That being said, I am looking for an inverter that will work for under $1000.

Regarding my heating elements. Each one has a label on it that gives the wattage. They range from 500 watts to 2000 watts The living room circuit has 4000 watts, What I plan on doing is installing switches on all the units and switching the larger ones off.

Otherwise I will use space heaters which have a draw a maximum of 1500 watts. I also have a indoor safe LP gas heater that will heat up to 1500 square feet. Therefore using the Prius generator to generate heat is not a big issue.

 

I have discovered an alternative to the transfer switch kit when using any back up generator that is:
a Generator interlock kit costing around $60-$70 as opposed to $300.

(Wikipedia)

A generator interlock kit (or just interlock kit) is a device designed to allow safe backfeeding of a home through a portable generator during power outages, thereby eliminating illegal and/or unsafe generator backfeeding situations that could potentially electrocute power linemen or destroy the generator.[1]

Operation
A generator interlock kit is installed on the front cover of the home's breaker panel. It consists of two sliding steel or plastic (depending on the brand) plates held together by three bolts. When moved down, the plate blocks the generator backfeed circuit breaker and allows the main breaker to remain on; when moved up, the generator backfeed circuit breaker may be turned on, but the main circuit breaker is blocked and will remain off. The generator backfeed circuit breaker is connected to a generator inlet installed (preferably) on the outside of the structure. A short cord connects the generator to the house inlet, usually through the use of L14-30 twist lock plugs and sockets. Determine the manufacturer of your main panel and purchase that companies interlock kit.

Advantages

• Using an interlock kit allows for all of a panel's circuits to be energized, up to the load capacity of the generator; whereas using a generator transfer switch only allows a few circuits to be operated.[2]
  
  
• An interlock kit does not require a separate panel to operate; it can be installed directly on the home's breaker panel.
  

• only allow the the generator breaker to be switched on if the main breaker is off
  
  
• not allow the main breaker to be turned on unless the generator breaker is off
  

Kits include top and bottom interlock plates, hardware, warning stickers, generator operation instructions, drill bit, and installation instructions.